When I left, the delay between me hitting the "save" button to post my de-adminship request on Meta and the sysop bit being removed was about 150 seconds. That included time spent indicating to the steward handling the request, via IRC, that I really did want to be de-adminned.
So I fail to see where this inability to block comes in. That's a lot quicker than the response time for the average AIV request, for example. The stewards know what to do; in an emergency, they would be able to act just as fast, if not faster.
The reason Stewards respond so quickly is because they don't have very much to do - everything is designed so that local admins and crats do as much of the work as possible. If it became necessary to desysop people much more often (as often as we currently block people, if the most radical suggestion were to be implemented), meta's requests for permissions page would become just like AIV. The solution would, of course, be creating more stewards. Once we've done that, the problem has just moved up a level.
Whatever you do, you have to have a small number of carefully selected people with more power than everyone else. What level of power you make the cutoff point is up to you, but you have to make it somewhere, and wherever you make it, you'll get the same complaints we're getting now about RfA. It's unfortunate that this is the case, but that's life.